1 . Field of the Invention
This invention relates to an automobile weight sensor for detecting the presence of a person having a weight in a car seat, and in particular to a sensor that can detect the presence of an occupant using strain sensitive resistors and provide an electrical signal to control activation of an airbag.
2 . Description of the Related Art
Various devices are well known for their ability to measure force, pressure, acceleration, temperature, position, etc. by using a sensing structure combined with signal processing electronics. One general type of sensor or transducer for such applications is a resistive strain gauge sensor in which force or pressure is sensed or measured based on strain placed on the resistors. Resistive strain gauges function by exhibiting changes in resistance proportional to force which causes dimensional changes of the resistor.
Many types of strain gauge sensors have been designed and made commercially available. Various strain gauge sensors have proven to be generally satisfactory. Prior art sensors, however, have tended to be rather expensive and not suitable in certain applications such as sensing the presence of an occupant in an automobile seat. A sensor suitable for such an application must be compact, robust, impervious to shock and vibration and yet inexpensive.
Automobile seats can use sensors to activate air bags, which would be deployed during an accident. Injury to infants or small children from air bag deployment with excessive force is a current industry problem. A weight sensor in the seat can be used to control the deployment force during air bag activation. If a heavy person is in the seat, the airbag is deployed at full force. If a light person is in the seat, such as a child, the airbag is deployed at a slower, less forceful rate or not at all. A current unmet need exists for a reliable, low cost, simple and robust automobile seat weight sensor that is used to control airbag deployment.
3 . Related Art
Examples of patents that are related to the present invention are as follows, and each patent is herein incorporated by reference for the supporting teachings:
U.S. Pat. No. 5,573,269 is a apparatus for sensing and restraining an occupant of a vehicle seat.
U.S. Pat. No. 4,556,598 is a porcelain tape for producing porcelainized metal substrates.
The foregoing patents reflect the state of the art of which the applicant is aware and are tendered with the view toward discharging the applicants acknowledged duty of candor in disclosing information which may be pertinent in the examination of this application. It is respectfully stipulated, however, that none of these patents teach or render obvious, singly or when considered in combination, the applicants claimed invention.
It is a feature of the invention to provide a reliable and cost-effective vehicle seat weight sensor for detecting the weight of a seat occupant. The sensor uses strain sensitive resistors.
An additional feature of the invention is to provide a vehicle seat weight sensor for sensing the weight of an occupant in a vehicle seat for use by an airbag control system. The seat has a seat back, a seat bottom and a seat bracket connected to a vehicle floor. A lower slide rail and an upper slide rail are coupled to the bracket and a seat pan is attached to the upper rail. The sensor includes a horizontally elongated substrate that is located between the seat bottom and the vehicle floor such that a portion of the weight of the seat occupant on the seat bottom is transferred from the seat bottom to the vehicle floor through the substrate. The substrate has a first and a second end. A neckdown region is formed in the substrate between the first and second ends for concentrating the weight of the vehicle occupant. Several strain gauge resistors are located on the neckdown region for generating an electrical signal in response to the substrate being stressed by the weight of the seat occupant. The electrical signal changes magnitude as a function of the weight of the seat occupant. The sensor can be located in several locations within the car seat. The substrate can be located between the upper slide rail and the seat pan. The substrate can be located between the lower slide rail and the seat bracket. The substrate can also be located between the lower seat rail and the vehicle floor. An additional feature of the invention is to provide a vehicle seat weight sensor for sensing the weight of an occupant in a vehicle seat. The sensor includes a substrate that has a first and second end. At least one strain gauge resistor is located on the substrate for generating an electrical signal in response to the substrate being stressed. The electrical signal changes as a function of the weight of the seat occupant. A connection mechanism is located at the first and second ends of the substrate to connect the substrate to the vehicle seat.
The invention resides not in any one of these features per se, but rather in the particular combination of all of them herein disclosed and claimed and it is distinguished from the prior art in this particular combination of all of its structures for the functions specified. Other features of the present invention will become more clear from the following detailed description of the invention, taken in conjunction with the accompanying drawings and claims, or may be learned by the practice of the invention.
There has thus been outlined, rather broadly, the more important features of the invention in order that the detailed description thereof that follows may be better understood, and in order that the present contribution to the art may be better appreciated. There are, of course, additional features of the invention that will be described hereinafter and which will form the subject matter of the claims appended hereto. Those skilled in the art will appreciate that the conception, upon which this disclosure is based, may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention.